4,027 research outputs found
Higher Winding Strings and Confined Monopoles in N=2 SQCD
We consider composite string solutions in N=2 SQCD with the gauge group U(N),
the Fayet--Iliopoulos term \xi \neq 0 and N (s)quark flavors. These bulk
theories support non-Abelian strings and confined monopoles identified with
kinks in the two-dimensional world-sheet theory. Similar and more complicated
kinks (corresponding to composite confined monopoles) must exist in the
world-sheet theories on composite strings. In a bid to detect them we analyze
the Hanany--Tong (HT) model, focusing on a particular example of N=2. Unequal
quark mass terms in the bulk theory result in the twisted masses in the N=(2,2)
HT model. For spatially coinciding 2-strings, we find three distinct minima of
potential energy, corresponding to three different 2-strings. Then we find
BPS-saturated kinks interpolating between each pair of vacua. Two kinks can be
called elementary. They emanate one unit of the magnetic flux and have the same
mass as the conventional 't Hooft--Polyakov monopole on the Coulomb branch of
the bulk theory (\xi =0). The third kink represents a composite bimonopole,
with twice the minimal magnetic flux. Its mass is twice the mass of the
elementary confined monopole. We find instantons in the HT model, and discuss
quantum effects in composite strings at strong coupling. In addition, we study
the renormalization group flow in this model.Comment: 41 pages, 11 figure
On Some Universal Features of the Holographic Quantum Complexity of Bulk Singularities
We perform a comparative study of the time dependence of the holographic
quantum complexity of some space like singular bulk gravitational backgrounds.
This is done by considering the two available notions of complexity, one that
relates it to the maximal spatial volume and the other that relates it to the
classical action of the Wheeler-de Witt patch. We calculate and compare the
leading and the next to leading terms and find some universal features. The
complexity decreases towards the singularity for both definitions, for all
types of singularities studied. In addition the leading terms have the same
quantitative behavior for both definitions in restricted number of cases and
the behaviour itself is different for different singular backgrounds. The
quantitative details of the next to leading terms, such as their specific form
of time dependence, are found not to be universal. They vary between the
different cases and between the different bulk definitions of complexity. We
also address some technical points inherent to the calculation.Comment: 24 pages, 6 figures. v2: minor correction
Confinement and Localization on Domain Walls
We continue the studies of localization of the U(1) gauge fields on domain
walls. Depending on dynamics of the bulk theory the gauge field localized on
the domain wall can be either in the Coulomb phase or squeezed into flux tubes
implying (Abelian) confinement of probe charges on the wall along the wall
surface. First, we consider a simple toy model with one flavor in the bulk at
weak coupling (a minimal model) realizing the latter scenario. We then suggest
a model presenting an extension of the Seiberg--Witten theory which is at
strong coupling, but all theoretical constructions are under full control if we
base our analysis on a dual effective action. Finally, we compare our findings
with the wall in a "nonminimal" theory with two distinct quark flavors that had
been studied previously. In this case the U(1) gauge field trapped on the wall
is exactly massless because it is the Goldstone boson of a U(1) symmetry in the
bulk spontaneously broken on the wall. The theory on the wall is in the Coulomb
phase. We explain why the mechanism of confinement discussed in the first part
of the paper does not work in this case, and strings are not formed on the
walls.Comment: 55 pp; v2: several remarks adde
Strings Inside Walls in N=1 Super Yang-Mills
We conjecture the existence of strings bounded inside walls in SU
Super Yang-Mills theory. These strings carry quantum number, where
is the greatest common divisor between , the charge of the wall, and
. We provide field-theoretical arguments and string-theoretical evidences,
both from MQCD and from gauge-gravity correspondence. We interpret this result
from the point of view of the low-energy effective action living on the
-wall.Comment: 25 pp. Major changes. In particular, following the recent work
arXiv:0807.1908 we have been able to give a field theoretical proof of the
statement. We have also corrected an important erroneous interpretation in
the previous version regarding the 2+1 effective action; Typo
Stable vs Unstable Vortices in SQCD
We give a topological classification of stable and unconfined massive
particles and strings (and some instantons) in worldvolume theories of
M5-branes and their dimensional reductions, generalizing Witten's
classification of strings in SYM. In particular 4d N=2 SQCD softly broken to
N=1 contains torsion (Douglas-Shenker) Z_N-strings and nontorsion (Hanany-Tong)
Z-strings. Some of the former are stable when the flavor symmetry is gauged,
while those that are not stable confine quarks and in some vacua even dyons
into baryons. The nontorsion strings are stable if and only if all colors are
locked to flavors, which is weaker than the BPS condition. As a byproduct
unstable string decay modes and approximate lifetimes are found. Cascading
theories have no vortices stabilized by the topological charges treated here
and in particular Gubser-Herzog-Klebanov axionic strings do not carry such a
charge.Comment: 32 pages, 6 figure
Compositional Performance Modelling with the TIPPtool
Stochastic process algebras have been proposed as compositional specification formalisms for performance models. In this paper, we describe a tool which aims at realising all beneficial aspects of compositional performance modelling, the TIPPtool. It incorporates methods for compositional specification as well as solution, based on state-of-the-art techniques, and wrapped in a user-friendly graphical front end. Apart from highlighting the general benefits of the tool, we also discuss some lessons learned during development and application of the TIPPtool. A non-trivial model of a real life communication system serves as a case study to illustrate benefits and limitations
Interplay of the volume and surface plasmons in the electron energy loss spectra of C
The results of a joint experimental and theoretical investigation of the C60
collective excitations in the process of inelastic scattering of electrons are
presented. The shape of the electron energy loss spectrum is observed to vary
when the scattering angle increases. This variation arising due to the electron
diffraction of the fullerene shell is described by a new theoretical model
which treats the fullerene as a spherical shell of a finite width and accounts
for the two modes of the surface plasmon and for the volume plasmon as well. It
is shown that at small angles, the inelastic scattering cross section is
determined mostly by the symmetric mode of the surface plasmon, while at larger
angles, the contributions of the antisymmetric surface plasmon and the volume
plasmon become prominent.Comment: 11 pages, 3 figure
Acoustic sensor to measure snowdrift and wind velocity for avalanche forecasting
A new mathematical model of slushflow dynamics is developed. A slushflow is treated as a two-layer flow. The lower layer consists of pure liquid phase (water) and the upper layer is a floating water saturated snow (slush). The equations of mass and impulse conservation for each layer are written. These equations include an interaction and mass exchange between the layers and between the water or slush layer and snow cover. The model equations were integrated numerically according to a developed for PC program. Series of numerical experiments for uniform slope were carried out. The structure and dynamics of slushflow were investigated. The dependencies of depths, velocities of flow and front coordinates of the upper and the lower layers on the parameters of the model are established. These parameters are the coefficient of snow entrainment, the coefficient of dry friction, the coefficients of turbulent friction, the discharge of water feeding at the rear end of flow, the snow cover thickness and the slope angle. An effect of exhaustion of the water layer is revealed. This effect is due to fast water absorption by entrained masses of snow
On The Problem of the Quantum Heterotic Vortex
We address the problem of non-Abelian super-QCD, with a Fayet-Iliopoulos
term, as seen from the vortex worldsheet perspective. Together with the FI term
, also a mass for the adjoint superfield enters in the game.
This mass allows the interpolation between and super-QCD. While
the phenomenology of the case () is pretty much understood, much
remains to be clarified for the finite- case. We distinguish, inside the
parameter space spanned by the FI term and the mass , four different
corners where some quantitative statements can be made. These are the regions
where the strong dynamics can, in some approximation, be quantitatively
analyzed. We focus in particular on two questions: 1) Is the quantum vortex BPS
or non-BPS? 2) What is the phase of the internal non-Abelian moduli? We find
that the answer to these questions strongly depends upon the choice of the
linear term in the superpotential. We also try to explain what happens in the
most unexplored, and controversial, region of parameters, that of the quantum
heterotic vortex, where .Comment: 47 pp; v2: typo
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